Tetris is part of Emacs.
It has a neat bug that allows even very slow people to play it: Push ‘p’ (for pause) and continue to play. The pieces stop dropping, but you can still move them around and drop them manually with the space bar.
And EmacSpeak advices it to enable on to play Tetris completely eye-free
If you dislike having the high-scores buffer popping up, when the game is over, you can add this to your ~/.emacs
(defadvice tetris-end-game (around zap-scores activate) (save-window-excursion ad-do-it))
If you don’t know what Tetris is (perhaps you’ve just returned from an interstellar journey), then see WikiPedia:Tetris.